Journal of Soil Science and Plant Nutrition, 2011, 11 (4), 129-137
Effects of topsoil loss on wheat productivity in dryland
zones of Chile
N. Brunel1*, F. Meza2, R. Ros3, F. Santibáñez4
Centro de Desarrollo para el Secano Interior, Universidad Católica del Maule, Talca, Chile. 2Universidad del
1
Mar, Sede Centro-Sur, Chile. 3Facultad de Ciencias Agrarias y Forestales, Universidad Católica del Maule,
Talca, Chile. 4Centro de Agricultura y Medio Ambiente, Universidad de Chile, Santiago, Chile. *Corresponding author: [email protected]
Abstract
Considering that the most important processes of biogeochemical cycles occur in
the upper first centimetres of the soil, minor degrees of erosion may affect crop
productivity, especially in the case of low input dryfarming production systems,
which dominate the central coastal areas of Chile. The purpose of this study was to
evaluate the effect of topsoil loss on wheat productivity in dryfarming areas with
Mediterranean climates in Central Chile. The experiment was conducted on a Chilean Alfisol (Pencahue; 35°18`53``S and 71°53`40``W), and the topsoil of this soil
was progressively removed from a depth of 2 to 18 cm (2, 6, 10, 14 and 18 cm).
Once the plots (25 m2) were prepared, winter wheat (Triticum aestivum L.; cultivar Pandora-INIA) was sown by applying the traditional techniques of the zone. A
design was established on randomised blocks with six treatments and three replications. After one growing season, the results showed significant differences (p<0.05)
in grain yield (kg ha-1) between the control treatment (T0) and the treatment with 18
cm of soil removed (T18) with productivity decreasing by 35%. Furthermore, most
of the considered productivity parameters were negatively correlated with the depth
of soil removed. The results highlighted the importance of topsoil fertility and depth
in crop yield.
Keywords: soil erosion, topsoil depth, desurfacing, Mediterranean climate.
129
130
Brunel et al.
1. Introduction
Wheat (Triticum spp.) is one of the main crops in dry-
rosity with various suppressing effects on crop yield
land areas worldwide. In Chile, approximately 70%
(Gollany et al., 1992; Malhi et al., 1994).
of wheat crops are established in areas with an arid
The depth of topsoil has proven to be a signifi-
to subhumid Mediterranean climate, which has an
cant parameter in determining soil quality and land
important role in the rural economies of broad areas
productivity. However, changes in the properties of
(Mellado, 2007). Most wheat growing areas are estab-
this horizon may produce unexpected crop responses
lished on granitic soils, mainly in the coastal moun-
because of a combination of indirect effects (Power et
tain areas of Central Chile, and 63% of these soils
al., 1981; Mielke and Schepers, 1986; Christensen and
are undergoing severe erosion processes (Pérez and
McElyea, 1988; Larney et al., 1995). Properties of the
González, 2001). Soil degradation is a consequence
soil profile and interaction of different processes gen-
of decades of dryfarming slope cultivation of cereals
erate a complex system influencing crop behaviour.
and overgrazing. Thus, many areas of soil have lost
Thus, it is not always possible to apply a simple and
their surface horizon and fertility, which has led to a
universal quantitative relationship to topsoil thickness
dramatic drop in wheat productivity and has reduced
and crop productivity (Gollany et al., 1992). Some au-
the income of poor rural populations.
thors have established linear and nonlinear relation-
The intensive tillage of these fragile soils has
ships between crop productivity and topsoil degrada-
triggered a process of degradation characterised by
tion, and they have suggested that not all soils behave
critical surface erosion, which degrades the upper
similarly with respect to erosion processes (Hairston
horizons and affects the topsoil depth and properties,
et al., 1988; Larney et al., 1995; Larney et al., 2000).
thereby, reducing their productive potential (Thomp-
The effect of soil loss may be explained with changes
son et al., 1991; Izaurralde et al., 2006). Nonethe-
in the chemical and/or physical characteristics of the
less, intensive production practices conceal the im-
soil and by its interactions that impact crop produc-
mediate effects of soil degradation, which makes
tion (Christensen and McElyea, 1988; Izaurralde et
early symptoms imperceptible or undetectable by
al., 2006; Thompson et al., 1991).
simple observation (Flörchinger et al., 2000; Malhi
One method commonly used to evaluate the ef-
et al., 1994; Bakker et al., 2004; Fenton et al., 2005;
fects of erosion on productivity is the removal of
Larney et al., 2009). During the erosion process
topsoil or “desurfacing”. This technique simulates an
in cultivated soils, the depth of the Ap horizon de-
erosive phenomenon, but the negative effects of this
creases and clay content increases as a consequence
approach may be exaggerated because of the abrupt-
of mixing with finer particles from lower horizons
ness of the disturbance (Larney et al., 2000; Bakker
due to tillage. In addition to being rich in clays, this
et al., 2004). To overcome this limitation and to allow
material has low levels of organic matter, and these
for more realistic results, these authors have proposed
characteristics are then transferred to the new upper
the removal of small amounts of soils in continuous
horizon during erosion (Frye et al., 1982; Chris-
intervals over a long period of time. In agricultural
tensen and McElyea, 1988). Furthermore, the loss of
areas with degraded soils and limited access to tech-
topsoil is followed by an increase in bulk density,
nology, slight levels of soil loss can result in a nega-
structural deterioration and alteration of the total po-
tive tendency of crop productivity. The objective of
Journal of Soil Science and Plant Nutrition, 2011, 11 (4), 129-137
Relationship between topsoil loss and wheat yield
131
this experiment was to evaluate the decline of winter
2008-2009 season in the locality of Pencahue, Maule
wheat (Triticum aestivum L.) productivity as a conse-
Region, Chile (35°18`53``S and 71°53`40``W). The
quence of topsoil loss in a dryfarming system located
site is within an agroecological zone of interior
in the subhumid Mediterranean climate area of the
dryland with a temperate subhumid Mediterranean
Maule Region in Chile.
climate, an annual average rainfall of 648 mm,
a maximum average temperature of 32.6 ºC and a
2. Materials and methods
minimum annual average temperature of 5.5 ºC (CIREN, 1997). The average ground elevation reaches
2.1. Characterisation of the study site
up to 207 m a.s.l., and the average slope is less than
To determine the effect of topsoil removal on wheat
3%. Rainfall distribution during the crop season is
productivity, a field trial was conducted during the
shown in Table 1.
Table 1. Rainfall during growing season (2009).
Month
Rainfall
(mm)
May
June
July
August
September
October
November
December
Total
77
126
53
107
31
41
22
0
457
The soil at the site is an Alfisol, which is classified
Table 2. Chemical properties of untreated topsoil
as a fine, mixed, and thermic Mollic Palexeralfs (Po-
(0-20 cm).
cillas Asociacion) (CIREN, 1997), and it has a sandy
clay loam texture and subangular blocky structure
in the upper horizon. The site is located in a valley
bottom positioned on alluvial-colluvial deposits. The
following four horizons are recognised in the profile:
Properties
Value
Total N (mg kg )
4
P (mg kg )
5
-1
-1
K (mg kg )
81
-1
Organic matter (%)
1.28
(18-35 cm; 7.5 YR 4/4 in moist conditions with the
pH
5.51
Ap (0-17 cm; 10 YR 4/2 in moist conditions); Bw1
presence of mottles); Bw2 (36-95 cm; 10 YR 3/2 in
-1
Mn (mg kg )
6.10
moist conditions with 30% mottles) and BC (96-120
Zn (mg kg )
0.56
cm; 7.5 YR 4/4 in moist conditions to 7.5 YR 4/2 in
Cu (mg kg )
2.93
Fe (mg kg )
44.02
moist conditions with a reduced presence of mottles).
Topsoil characteristics prior to desurfacing based on
six subsamples randomly selected within each plot
(Table 2) were determined by soil analysis using the
methodologies described by Sadzawka et al. (2006).
-1
-1
-1
B (mg kg-1)
0.24
Ca (cmol kg )
7.21
Mg (cmol kg )
2.04
-1
-1
Journal of Soil Science and Plant Nutrition, 2011, 11 (4), 129-137
132
Brunel et al.
2.2. Field methods
determination
and
yield
parameter
2.3 Experimental design and statistical analysis
The experimental design was based on randomised
In November 2008, 18 plots (5 m x 5 m) were cre-
blocks with six treatments (five levels of soil removal
ated by removing increasingly thicker topsoil lay-
plus a control without soil removal) with three replica-
ers as follows: 2, 6, 10, 14 and 18 cm (T2 to T18
tions. Analysis of variance was performed to determine
treatments). Furthermore, a control treatment (T0)
if there was an effect of soil removal on the considered
with unaltered soil was established. The removal
target variables. Comparison of means was performed
of the first 2 cm of soil was done manually, and the
according to Tukey’s test using IBM SPSS v.18 software.
remaining treatments were set mechanically using
a skid steer loader (Bobcat brand, model S130,
3. Results and discussion
USA). The soil was kept under traditional fallow
until May 2009, and it was then prepared with a
The results obtained for the first growing season
Honda rototiller (model F600). An equivalent seed
showed a proportional decreasing trend in wheat
dose of 220 kg ha per plot of Triticum aestivum
yield according to the different levels of soil removed
(Variety Pandora-INIA) was scattered without fer-
with major differences between T0 and T18 as shown
tiliser application. In late July, soil macro- and
by the analysis of variance (Tables 3 and 4). Grain
micronutrients were analysed from samples taken
yield (kg ha-1) was significantly reduced in proportion
at a 0-20 cm depth after the soil was removed for
to the level of topsoil removal (p<0.05). Similarly, the
all six treatments using methodologies previously
1000 grain weight and grains per spike parameters
described by Sadzawka et al. (2006). At the time
decreased with increasing soil removal, and biomass
of physiological maturity, the wheat was harvested
yield showed no significant difference among treat-
at ground level, and samples were collected from
ments (Table 3). These results differed from those ob-
an area of one m2 at the centre of each plot. A sam-
tained by Izaurralde et al. (2006) who demonstrated
ple of 50 spikes was oven-dried at 70 °C for 48 h
marked effects on total dry matter yield according to
and then weighed. Dry weight was used to deter-
simulated erosion levels. Nevertheless, in areas with
mine grain yield (kg ha ), biomass yield (kg ha ),
arid to subhumid Mediterranean climate, such as in
1000 grain weight (g), spikes (m-2) and grains per
the coastal mountains of Central Chile, the rainfall
spike. Furthermore, a complete grain analysis was
distribution showed a marked peak between May
carried out using the methodologies described by
and August (Table 1) followed by a sharp decrease
Sadzawka et al. (2001).
in spring, thus, limiting soil water availability during
-1
-1
-1
the grain filling period, and this climatic condition affected grain yield more than total biomass production.
Journal of Soil Science and Plant Nutrition, 2011, 11 (4), 129-137
Relationship between topsoil loss and wheat yield
133
Table 3. ANOVA for target production parameters.
Parameters
Sum squares
Dof
Quadratic means
Sig.
Biomass (kg ha )
3402824
5
680564
.095
Grain yield (kg ha-1)
457260
5
91452
.000
0.007
5
.001
.494
-1
Harvest index
1000 grain wg (g)
37.387
5
7.4
.000
Spikes m-²
35428.484
5
7085
.208
Grain m-²
1836273
5
367254
.001
Number of grains per spike
135.350
5
27
.005
Grain weight per spike (g)
.267
5
.053
.003
(Sig. < 0.05 means significant difference.)
Table 4. Effect of topsoil removal on productivity parameters of winter wheat (Triticum aestivum; cultivar
Pandora-INIA).
Treatment
(cm)
Grain yield
(kg ha-1)
1000 grain
wg (g)
Grain
m-²
Grain number per
spike
Grain weight
per Spike (g)
T0
1176 a
41.2 a
2853 a
15 a
0.62 a
T2
1046 ab
42.2 a
2478 ab
10 a
0.44 ab
T6
1095 ab
40.7 ab
2693 ab
10 a
0.40 b
T10
1080 ab
40.5 ab
2664 ab
9a
0.37 b
T14
852 ab
39.0 bc
2181 ab
7 ab
0.28 b
T18
770 b
37.8 c
2032 b
8b
0.30 b
Measured values accompanied by different letters in the same column indicate significant differences according
to Tukey’s test (p<0.05).
Significant differences (p<0.05) in grain yield (kg ha-1)
may be a consequence of lower grain weight and pro-
between T0 and T18 (Table 4) were observed. The re-
duction, which result in the concentration of nitrogen
moval of 18 cm of topsoil reduced grain yield by 35%
compounds. The other analysed nutrients in the wheat
as compared with T0. This result was similar to the
grain showed no significant differences among treat-
39% reduction obtained by Larney et al. (2000) for 15
ments. The decrease in grain yield was closely related
cm of topsoil removal and 44% reduction obtained by
to grain weight, and this last parameter was that most
Tanaka and Aase (1989). These authors also observed
affected by soil removal with a high level of corre-
a decrease in grain nitrogen content, which differed
lation (R2=0.71). The results showed a reduction in
from the results obtained by Izaurralde et al. (2006)
grain weight by 6.5% on average between both T14
and those observed in this study where the amount
and T18 with respect to T0, and these results were in
of N increased by 18% in the wheat grain for T18 as
agreement with those obtained by Izaurralde et al.
compared with T0 (1.13 vs. 1.38%). This observation
(2006).
Journal of Soil Science and Plant Nutrition, 2011, 11 (4), 129-137
134
Brunel et al.
The values for grain yield (kg ha-1), 1000 grain
ity. For every 1 cm of removed topsoil, there was a
weight and grains per m2 were highly correlated
corresponding decrease of 24 kg ha-1 in grain yield
with soil removal unlike biomass yield and spikes
(R2=0.75). The use of fertilisers and manure in high
per m2, which showed no significant correlation.
levels masked the low soil productivity. Without fer-
Figure 1 shows the regressions between the main
tiliser application, the obtained results indicated low
yield components and the different levels of soil re-
crop yields in a zone resulting from centuries of soil
moval. The linear function of grain yield and topsoil
loss events, which has been estimated to be 29.95 Mg
removal showed a critical drop in wheat productiv-
ha-1 year-1 (Pérez and González, 2001).
Figure 1. Correlation plot: productivity parameters vs. topsoil removal.
Journal of Soil Science and Plant Nutrition, 2011, 11 (4), 129-137
Relationship between topsoil loss and wheat yield
135
As a consequence of topsoil removal, the reduction
critical during the grain filling period, which occurs
in grain yield associated with the effect observed for
during a time of higher evapotranspiration demand
grain weight may be related to a water deficit during
and lower precipitation occurrence. On the basis of
the reproductive period, and this impact was higher
a series of studies, Den Biggelaar et al. (2001) de-
with more soil removal. The low fertility status and
termined that the yield decline in eroded plots in dry
low water retention were magnified by the low or-
years is more significant than in years with abundant
ganic matter content (Table 5). This is especially
rainfall.
Table 5. Soil analysis for treatments after topsoil removal.
T
N
P
K
O.M.
%
pH
Mn
Zn
B
------------ mg kg ------------
Ca
Mg
Silt
Clay
%
%
%
---- mg kg ----
T0
12
7
96
1.60
6.22
4.03
0.50
0.34
6.32
1.81
52
26
23
T2
10
5
85
1.25
6.12
3.81
0.39
0.15
7.16
1.95
51
27
23
T6
8
5
93
1.05
6.22
3.89
0.71
0.15
6.92
1.97
50
26
25
T10
9
5
84
1.11
6.26
3.70
0.32
0.15
7.11
1.91
51
25
25
T14
13
4
74
1.05
6.31
2.21
0.25
0.16
8.13
2.33
51
23
27
T18
11
4
87
0.98
6.48
1.87
0.22
0.15
10.24
3.02
45
25
31
-1
--- cmol kg ---
Sand
cm
-1
-1
(The following abbreviation is used: OM, organic matter content)
Several factors can affect crop yield as result of the
more severe in degraded dryland soils because the up-
interaction of the effects of topsoil loss. Oyedele and
per horizons have already been severely diminished
Aina (2006) concluded that the primary impacts of
and few fertile materials rise towards the surface.
soil removal more significantly affects soil physi-
Both of these factors are directly related to the effects
cal properties and organic matter content than other
of soil erosion (Frye et al., 1982; Larney et al., 1995).
chemical properties. In contrast, other studies con-
Organic matter content is one of the properties
ducted on soils to simulate erosion have found that
mainly affected by erosion because the concentration
nutrient deficiency is the main factor in yield reduc-
of organic carbon is consistently higher in the first 15
tion with drastic changes observed in the chemical
cm of the soil profile (Bauer and Black, 1994). The
properties of soil in relation to the depth of removed
reduction in organic matter due to topsoil removal
soil (Larney et al., 2000; Izaurralde et al., 2006).
and its impact on crop productivity has been docu-
As shown in Table 5, the soil analysis after topsoil
mented in other studies (Malhi et al., 1994; Gollany et
removal showed that the remaining horizon had lower
al., 1992; Izaurralde et al., 2006; Oyedele and Aina,
contents of organic matter and micronutrients, such
2006). In terms of soil productivity, Bauer and Black
as Mn, Zn and B, as compared with the original soil.
(1994) estimated that the contribution of 1 Mg ha-1 of
These results revealed the preliminary effects of top-
organic matter in the upper 30.5 cm is equivalent to
soil loss associated with the exposure of the lower ho-
35.2 and 15.6 kg ha-1 of biomass and grain yield, re-
rizons. Thus, the impacts of topsoil loss will be even
spectively. In this study, the decrease in organic mat-
Journal of Soil Science and Plant Nutrition, 2011, 11 (4), 129-137
136
Brunel et al.
ter content between T0 to T18 (0.62%) corresponded
tant role in establishing the shape of this function. In
to a loss of approximately 15.84 Mg ha-1 between 0
general, these results obtained from dryland areas in
and 18 cm given that the soil bulk density was equal
Central Chile highlighted the importance of topsoil
to 1.42 Mg m-3, which would have a direct impact on
where physical, chemical and microbiological factors
crop productivity.
may be critical in defining the decay function of crop
For organic matter and clay percentages, the dif-
productivity and soil loss.
ferences observed were even greater at a depth below
14 cm. The topsoil removal in these treatments (T14-
Acknowledgements
T18) resulted in an average decrease in organic matter
(36%) and an increase in clay (19%). Consistent with
This research was funded by the Dirección de In-
data obtained by Gollany et al., (1992), the increment
vestigación y Perfeccionamiento de la Universidad
in clay content in T18 can be explained by the expo-
Católica del Maule. The authors thank Dr. Oscar Seg-
sure of the Bw1 horizon of the original pedon. In turn,
uel from the Universidad de Chile and Dr. Iván Matus
the increase in the clay fraction may be associated
from INIA Quillamapu for their selfless support of the
with the higher concentrations of Ca and Mg ions
investigation. The authors would also like to thank the
in the soil, which may explain the increase of these
Centro de Desarrollo del Secano Interior from UCM
exchange bases deeper within the profile. Despite that
for their technical support.
2+
2+
topsoil loss due to water erosion is imperceptible each
year and is not a uniform phenomenon, the result of
this study demonstrated that the low crop productivity
in the study area is due to hundreds of years of soil
degradation.
4. Conclusions
In this study, the wheat grain yield had a proportional decreasing trend with respect to the levels of
soil removed. However, the results obtained for one
growing season only presented statistical differences
for excessive soil loss (>2000 Mg ha-1). Removal of
18 centimetres of soil resulted in the loss of a fertile
layer within the soil profile (0-15 cm), which was reflected by a 36% reduction in organic matter content
in this study. The effects on the physical properties
of soil, mainly on available water storage, are factors that influence this relationship, and these effects
must be evaluated. Similarly, agroclimatic conditions,
References
Bakker, M., Govers, G., Rounsevell, M. 2004. The
crop productivity–erosion relationship: an analysis based on experimental work. Catena 57, 55-76.
Bauer, A., Black, A. 1994. Quantification of the effect
of soil organic matter content on soil productivity.
Soil Sci. Soc. Am. J. 58, 185-193.
CIREN. 1997. Descripciones de suelos, materiales y
símbolos. Estudio Agrológico VII Región. Publicación N° 117. Centro de Información de Recursos Naturales. Chile. 659 p.
Christensen, L., McElyea, D. 1988. Toward a general
method of estimating productivity–soil depth response relationships. J. Soil Water Cons. 43, 199202.
Den Biggelaar, C., Lal, R., Wiebe, K., Breneman,
V. 2001. Impact of soil erosion on crop yields in
North America. Adv. Agron. 72, 1-52.
especially rainfall patterns, may also have an impor-
Journal of Soil Science and Plant Nutrition, 2011, 11 (4), 129-137
Relationship between topsoil loss and wheat yield
137
Fenton, T. E., Kazemi, M., Lauterbach-Barrett, M.
2005. Erosional impact on organic matter content
and productivity of selected Iowa soils. Soil Till
Res. 81, 163-171.
Malhi, S., Izaurralde, R., Nyborg, M., Solberg, E.
1994. Influence of topsoil removal on soil fertility
and barbey growth. J. Soil Water Cons. 49, 96101.
Flörchinger, F. A., Leihner, D. E., Steinmüller, N.,
Müller-Sämann, K., El-Sharkkawy, M. 2000. Effects of artificial topsoil removal on Sorghum,
Peanut, and Cassava yield. J. Soil Water Cons. 55,
334-339.
Mellado, M. 2007. El trigo en Chile. Cultura, ciencia
y tecnología. INIA Nº 21. Instituto de Investigaciones Agropecuarias. Chile. 684 p.
Frye, W. W., Ebelhar, S. A., Murdock, L. W., Blevins,
R. L. 1982. Soil erosion effects on properties and
productivity of two Kentucky soil. Soil Sci. Soc.
Am. J. 46, 1051-1055.
Gollany, H. T., Schumacher, T. E., Lindstrom, M.
J., Evenson, P. D., Lemme, G. D. 1992. Topsoil
depth and desurfacing effects on properties and
productivity of a typic argiustoll. Soil Sci. Soc.
Am. J. 56, 220-225.
Hairston, J. E., Sanford, J. O., Rhoton, F. E., Miller, J.
G. 1988. Effect of soil depth and erosion on yield
in the Mississippi blacklands. Soil Sci. Soc. Am.
J. 52, 1458-1463.
Izaurralde, R. C., Malhi, S. S., Nyborg, M., Solberg,
E. D., Quiroga, M. C. 2006. Crop performance
and soil properties in two artificially eroded soil in
North-Central Alberta. Agron. J. 98, 1298-1311.
Larney, F. J., Izaurralde, R. C., Janzen, H. H., Olson,
B. M., Solberg, E. D., Lindwall, C. W., Nyborg,
M. 1995. Soil erosion-crop productivity relationships for six Alberta soils. J. Soil Water Cons. 50,
87-91.
Larney, F. J., Olson, B. M., Janzen, H. H., Lindwall,
C. W. 2000. Early impact of topsoil removal and
soil amendments on crop productivity. Agron. J.
92, 948-956.
Larney, F. J., Janzen, H. H., Olson, B. M., Olson, A. F.
2009. Erosion–productivity–soil amendment relationships for wheat over 16 years. Soil Till Res.
103, 73-83.
Mielke, L. N., Schepers, J. S. 1986. Plant response to
topsoil thickness on an eroded loess soil. J. Soil
Water Cons. 41, 59-63.
Oyedele, D. J., Aina, P. O. 2006. Response of soil
properties and maize yield to simulated erosion
by artificial topsoil removal. Plant and Soil. 284,
375-384.
Pérez, C., González, J. 2001. Diagnóstico sobre el estado de degradación del recurso suelo en el país.
Boletín INIA N°15. Instituto de Investigaciones
Agropecuarias. Chile. 196 p.
Power, J. F., Sandoval, F. M., Ries, R. E., Merrill, S.
D. 1981. Effects of topsoil and subsoil thickness
on soil water content and crop production on a
disturbed soil. Soil Sci. Soc. Am. J. 45, 124-129.
Sadzawka, A., Grez, R., Mora, M., Saavedra, N.,
Carrasco, A. 2001. Métodos de análisis de tejidos
vegetales. Comisión de Normalización y Acreditación Sociedad Chilena de la Ciencia del Suelo.
Chile. 35 p.
Sadzawka, A., Carrasco, M., Grez, R., Mora, M.,
Flores, H., Neaman, A. 2006. Métodos de análisis
recomendados para los suelos de Chile. Serie N°
30. Centro Regional de Investigación. Chile. 164 p.
Tanaka, D. L., Aase, J. K. 1989. Influence of topsoil
removal and fertilizer application on spring wheat
yields. Soil Sci. Soc. Am. J. 53, 228-232.
Thompson, A. L., Gantzer, C. J., Anderson, S. H.
1991. Topsoil depth, fertility, water management
and weather influences on yield. Soil Sci. Soc.
Am. J. 55, 1085-1091.
Journal of Soil Science and Plant Nutrition, 2011, 11 (4), 129-137